What Causes Swollen Lymph Nodes Under The Neck?

one of my lymph nodes under my neck is swollen. In turn what I think is a salivary gland under my tongue on the same side is swollen. when I push on my lymph node it seams that the glad fills up. It also looks like there is a small, puss, bump in the gland. This is not the first time that this has happened but as I am reading various articles on this, it has the potential the be something bigger than I may think